Short wave converter



J1me 13, 1933. J, c, ROBERTS 1,914,165

SHORT WAVE CONVERTER Original Filed April 24, 1929 2 Sheets-Sheet l Juhe 13,1933; J, c. ROBERTS I 1,914,165.

SHORT WAVE CONVERTER originalF'iled April 24, 1929 2 Sheets-Sheet 2 -1111 2: n: I 4. INSULATION INEULATION INVENTOR JuZzIa/n 0. Robert;

\ B w fwmb Patented June 13, 1933 ears .FFECE JULIAN -c. noBnnirS, or MIAMI, FLORIDA, Assrsnon TO WEST SIDE RADIO LABonA, ronIns, me, or MIAMI, FLORIDA, A oonronATIon or FLORIDA snon'r WAVE CONVERTER Application filed April 24, 1929, Serial No. 357,680. Renewed September 7, 1932.

' particularly useful in adapting broadcast receivers for the reception of short waves. By the use of my invention a broadcast receiver having a tuning range from 200 to 550 meters may be employed for the reception of much shorter wave lengths, for example,

waves from 18 to meters.

An object of the invention is to devise an auxiliary short wave receiving device adapted to be permanently connected to a radio receiver of standard make and form a part thereof whereby the tuning range of the standard receiver may be extended into wave length bands outside of the tuning range of the standard set.

A further object of the invention is to devise an auxiliary short wave receiving device including tuning means, a detector, and detachable connector elements adapted to connect the auxiliary receiver to the input of the audio frequency amplifier'of a standard broadcast receiver.

The tuning converter which I have devised comprises a tuning element, a frequency changer for heterodyning with the received wave, a beat frequency amplifier for amplifying the beat wave from the frequency changer, a detector for detecting the audio frequency modulation carried by the beat wave, and connector elements for connecting the output of the detector to the input of the audio frequency amplifier of a standard broadcast receiver.

My invention is illustrated in the accompanying drawings in which Figure 1 shows one example of the standard receiver to which my invention may be applied;

Figure 2 is a diagram of my short wave converter for adapting the standard receiver to the reception of short waves;

Figure 3 is a top plan of one of two connectors used to connect the short Wave converter permanently to the standard receiver;

Figure 4 is a section taken on theline 4-4 of Figure 3; i

Figure 5 is a side elevation of one of the tubes of thestandard receiver partly seated in its socket, with the connector shown in Figure 4 interposed between said socket and the base of the tube;

Figure 6 is a top plan of the other connector used to connect the converter to the standard set; I

' Figure 7 is a section taken on the line 77 of Figure 6 and Figure 8 is a fragmentary side elevation of another tube ofthe standard set partly inserted in its socket and having the second connector arranged between the tube and socket.

Referring to Figure 1, there is shown a circuit diagram of one type of standard broadcast receiver to which my invention may be applied. The broadcast receiver comprises two radio frequency amplifiers Al and A2, a detector D1, two audio frequency amplifiers A3 and A4, and a loud speaker LS connected in theroutput circuit of the last audio frequency amplifier. The filaments of the vacuum tubes are supplied with heating current from the secondary of a transformer T1, the primary of which is energized from a source of alternating current AC. The input circuit of each radio frequency amplifier and the detector includes a tuned circuit by which the set may be tuned to any wave length within the broadcast band. The filament terminal of all the input circuits are connected together and to ground, and to the center tap of the secondary of transformer T1, by means of wire (a). The plate current for each vacuum tube is supplied from a rectifier R which is energized from the source of alternating current AC. The low voltage terminal of rectifier R is connected to the midpoint of the secondary winding of transformer T1 as shown.- The low voltage positive terminal of rectifier R supplies plate current to the detector D1. The intermediate voltage terminal of rectifier R supplies plate current to the radio frequency amplifiers A1 and AQ and to the first audio frequency amplifier A3, while the high voltage terminal of the rectifier supplies plate current to the last audio frequency amplifier.

' Referring to Figure 2, the short wave converter com rises a frequency changer HD, two ampli ers A5 and A6, a detector D2, and two connector units C1 and C2. While I have shown heater type vacuum tubes in Figure 2, it will be understood. that ordinary three-element filamentary cathode type of tube may be employed if desired. The heaters of the vacuum tubes shown in Figure 2 are connected in parallel and are supplied with heating current from the same source of alternating current AC which supplies operating current to the standard receiver shown in Figure 1. The input circuit of the fre quency changer HD includes a tuned circuit comprising secondary winding S, with a variable condenser C in shunt therewith. The constants of this tuned circuit are so chosen that the circuit may be tuned to wave lengths within the band which it is desired to receive. The tuned circuit is energized from antenna A by a magnetic coupling with primary winding P, which is included in the antenna circuit. The input circuit of the frequency changer HD also includes a grid condenser and a grid leak in shunt thereto. A tickler coil T is included in the plate circuit of the frequency changer and is coupled with the tuned circuit SD in proper direction to produce sustained oscillations of a frequency determined by the tunin of the tuned circuit.

A variable condenser is provided to con trol the amount of feed-back. T1, T2, and T3 are special iron-cored transformers designed to transmit efficiently waves of a frequency of the order of 30 kilocycles. The input circuit of detector D2 includes a grid condenser and a grid leak in shunt thereto. C1 is a detachable connector element comprising a flat disc of insulating material having holes P, F, F, K and G corresponding to the plate, filament, cathode, and grid prongs on the detector tube D1 of the standard set shown in Figure 1.

The connector element G1 has the holes K and I made slightly larger than the grid and filament holes G and F in order to receive snugly the conductor plates 3 and 4 having spring sockets 5 and 6 formed on their respective ends at right angles thereto. These sockets 5 and 6 are split and are made of springy material so that they may fit snugly within the holes P and K and be retained therein by friction. The sockets 5 and 6 are of the same internal diameter as the grid and filament holes in the connector C1, and are adapted to receive the cathode and plate prongs of the detector tube D1. This connector Cl is interposed between the base of the detector D1 and the socket D8 designed to receive it in the standard broadcast set. The plates 3 and 4 and the sockets formed therein are made of suitable conducting material. The conductor plate 3 is connected by wire 7 to the heater cathodes of the converter; and is also connected by wire 8, to the heater cathode of the detector D1. The conductor plate 4: is connected by the wire 11 to the plate of the detector tube D2 of the converter, and this wire 11 is connected by a'wire 12 to the plate r of the detector D1 inthe standard broadcast receiver.

The connector C2 is interposed between the base of the amplifier A2 and the socket A28 thereof. This connector C2 is provided with the apertures P1, G1, F1 and F2, lo-

.cated to receive the prongs of the amplifier tubular member 13 is such that it forms conducting contact with the plate prong of the amplifier tube A2. The conductor plate 1 1 of the connector C2 is connected by the wire 15 to the plate of the amplifier A2 in a standard broadcast set. manently located between the base amplifier A2 and the socket A2s-so that ordinarily this connector as well as the connector C does not interfere with the normal operation of the amplifier tube [12 and the detector tube D1.

In stating thatthe connectors C1 and C2 are permanently connected to the standard receiver, it must of course be understood that this means that the connectors are not designed to be removed every time it is desired to tune in the short waves from the converter through the detector D1 and the succeeding audio frequency amplifiers and loud speaker of the broadcast set. This description is merely intended to distinguish the present invention from others which include a short wave converter that can be used only by a separate plug-in connection which involves removal of one of the tubes of the standard set and insertion thereof into a scparate socket especially provided for it on the converter apparatus. In other words, the present invention is designed to be permanently connected to a standard broadcast receiver so that the apparatus as a whole can be tuned to receive on either long or short waves without involving the removal of any of the parts of either the converter or standard set from their normal operative position.

The connector C2 is per- From an inspection of the drawings it will 5 i be seen that the cathodes of the tubes shown in Figure 1 areconnected to the cathode of detector D1, which is connected to the negative terminal of rectifier R. Also, the plate I I circuits of tubes HD, A5 and A6 are connected to the plate element of amplifier A2, which is connected to the positive intermediate voltage terminal of the rectifier It, and the plate element of detector D2 is connected to the plate of detector D1, which is con- 13 nected to the low voltage positive terminal of rectifier R through the primary winding of the first audio frequency transformer in Figure 1. Thus, plate currents of proper 53 voltages are supplied to the various tubes in Figure 2 from the rectifier associated with the standard set in Figure 1 by way of the connections provided by connector elements Cl and C2. A variable resistance 6 is connected across the input circuit of amplifier A6 to control the volume of the received signal.

Operation of the invention is as follows:

As explained above, transformers T1, T2 and T3 are designed to transmit waves of a frequency of the order of kilocycles. The tunable input circuit of the frequency changer HD is adjusted until the oscillations generated by it differ in frequency from the desired incoming wave by approximately 30 kilocycles. The frequency changer I-ID combines the incoming wave with the locally generated wave to produce a beat frequency wave of approximately 30 kilocycles, which varies in amplitude in accordance with the signal carried by the incoming wave. This beat frequency is then amplified by amplifiers A5 and A6 and supplied to the input circuit of detector D2. The action of detector D2 is to demodulate the beat wave and to derive therefrom low frequency currents corresponding to the signal carried by the ins coming wave. The output of detector D2 is supplied to the input of audio amplifier A3 of the standard set shown in Figure 1 through the connections established by connector elements C1 associated with the detector tube D1. The detected signal is then amplified by amplifiers A3 and A4, and is finally reproduced in the loud speaker LS of the standard set.

From the foregoing it will be seen that I have devised a short wave converter employing amplifying and detecting tubes, and wherein the filament and plate operating currents for the tubes of the converter are supplied from the same source which supplies the standard broadcast receiver.

By employing the particu ar form of connector elements C1 and 02, it is not necessary for the detector D1 and amplifier A2 to be removed from the receiving set While the short wave converter is in operation. By this arrangement the receiving set may be easily and quickly changed to receive either on the roadcast range or on the short wave range. It will be understood that While the short wave converter is in operation, no broadcast Waves are being received on the standard receiver. This condition may be obtained in any desired way, such as by disconnecting the antenna from the standard set, by tuning the standard receiver to a position where waves of the standard broadcast length are not re- 7 ceived, and sometimes by manipulation of a which the plate circuits are supplied with rectified alternating current, it is to be understood that my short wave converter may be applied to receiving sets of the type in which both the filament and platecircuits are supplied with direct current from suitable batteries. It is also apparent that direct current may be employed to energize the filaments of the thermionic relays in the short wave converter.

Having thus described my invention, what I claim is:

1. In a radio receiving system, the combination of a radio receiving set adapted to receive waves in a given band of Wave lengths and including a radio frequency amplifier, a detector, a power supply source; an auxiliary receiving set adapted to receive wave lengths in a band different from that of said first set including a high frequency amplifier and a detector, a connection between the anode of the auxiliary detector and the anode of the main detector, and a connection between the anode of the auxiliary high frequency amplifier and the anode of the high frequency amplifier in the main set,

2. In a radio receiving system, the combination of a radio receiving set adapted to receive waves in a band of wave lengths and including a radio frequency amplifier, a detector, and a power supply source, an auxiliary receiving set adapted to receive wave lengths in a band different from said first set, and including a frequency changer, and a detector, a connection between the plate elements of the two detectors, and a connection between the plate element of the frequency changer and the plate element of the radio frequency amplifier in the main set, whereby plate current is supplied to the tubes in the auxiliary set through the plate circuits of the detector and the radio frequency amplifier of the main set. V a

3. In a radio receiving system,'the combination of a radio receiving set adapted to receive Waves in a band of wave lengths and including a radio frequency amplifier, a detector, and a power supply source, an auxiliary receiving set adapted to receive wave lengths in a band different from that of said first set and including a frequency changer, and a detector, a connection between the plate elements of the auxiliary and main detectors, the cathode of said frequency changer being connected to the cathode of the main detector, and a connection between the plate element of the frequency changer and the plate of the radio frequency-amplifier in the main set, whereby plate current is supplied to the tubes in the auxiliary set through the plate circuits of the detector and amplifier of the main set.

4.111 a radio receiving system, the combination of a radioreceiving set adapted to receive waves in a given band of wave lengths and including a radio frequency amplifier, a detector, an auxiliary receiving set adapted to receive wave lengths in a band different from the band of said first set and including a frequency changer, and a detector, and connections coupling the output circuits of the detector and frequency changer in the auxiliary set to the output circuits of the detector and radio frequency amplifier, respectively, of the main set.

5. In a radio receiving system, the co1nbination of a main radio receiver adapted to receive Waves in a given band and includin g a power suppl source, a radio frequency amplifier tube and a detector tube, with a converter including an oscillator tube and a detector tube, and means interposed between the sockets and tubes of the main receiver and permanently connected to the plate and heater elements of the converter tubes to supply operating energy from said source to the said elements.

6. In a radio receiving system, the combination of a main radio receiving set adapted to receive waves in a given band of wave lengths and including a radio frequency tube, a detector tube, an auxiliary radio receiver adapted to receive wave lengths in a band different from the band of said first set, and a connection fixed between said tubes and their sockets for permanently coupling the output circuit of the auxiliary set to the tubes of the main set without affecting the operative arrangement of the elements of either set.

7. In a radio receiving system, the combination of a main radio receiving set adapted to receive waves in a given band of wave lengths and including a radio frequency tube, a detector tube, an auxiliary radio receiver adapted to receive wave lengths in a band different from the band of said first set, a connection fixed between said tubes and their sockets for permanently coupling the output circuit of the auxiliary set to the tubes of the main set without affecting the operative arrangement of the elements of either set, and a single source of power supply for said tubes and said auxiliary receiver.

In testimony whereof I ailix my signature.

JULIAN C. ROBERTS. 

